The upcoming season of "Chicago Fire" will be disheartening for fans of Dawson (Monica Raymund) and Mills (Charlie Barnett).

Executive producer Danielle Gelber told TVLine that the Dawson and Mills relationship is over. "They're over in terms of they don't get back together," Gelber confirmed. "But there's still underlying feelings of a difficult breakup that we will play inter-personally between them. And we'll watch them both become involved with other people."

Severide (Taylor Kinney) will also be striking up a relationship with a new woman, but not in the way one may think. Severide will suspect that a 19-year-old named Katie is his father's very young mistress. He is shocked when he find out that Katie is--big spoiler-- Benny's (Treat Williams) daughter, making her Severide's sister.

Gelber recently hinted, "There's going to be layers of Severide's past that are revealed through Benny and through some unexpected twists." Severide discovering he has an estranged sibling is definitely one such twist.

The second season will also feature Casey (Jesse Spencer) still reeling after the death of his girlfriend, Hallie (Terri Reeves), who was killed in a fire at the hospital where she worked as a physician. Although Casey will still be mourning her death, he will begin to cope with the tragedy.

Jesse Spencer told TV Line that Casey finds "inner peace" about his girlfriend's death. Spencer said that Casey "develops a relationship with a couple of kids that he has to look after, and they help him through some difficult times, and he helps them. It's nice. It's an appropriate ending to the Hallie story."

After calling it quits with Mills, Dawson may strike up a relationship with the newly available Casey, a person she flirted with when he was taken. Yet, the possible hook-up will not happen immediately.

"They have a mutual understanding between each other," Spencer said. "There's an attraction, but there's a professionalism. They kind of put it to bed. You know as well as I do it's going to resurface at some point - and probably sooner rather than later. [But] right now, they're just friends."

In addition to Casey, EMT Shay (Lauren German) is also going through personal strife.

Shay has not been successful in her pregnancy attempts. Last season, she found out that her perspective sperm donor, Severide, fathered a child with another woman. Yet, Gelber said that Shay is "inherently a very strong person," and will persevere.

Instead of Shay expecting, viewers may see Renee (Sarah Shahi) with a bun in the oven.

The second season of "Chicago Fire" will return to NBC on September 24.